This invention relates to improvements in an electric power steering system for an automotive vehicle, in which a steering force of a driver is assisted by an electric motor.
In a conventional power steering system, a so-called dual pinion type electric power steering system is disclosed in Japanese Patent Provisional Publication No. 2002-154442. In the dual pinion type electric power steering system, a steering torque from a driver and an assist torque generated by a motor are respectively provided to separate pinions, thereby providing a merit of decreasing load to be applied to the pinions.